Chapter 1. Introduction

1. DATA COMMUNICATIONS

• Telecommunication: communication at a distance• Data: information presented in whatever form is

agreed upon by the parties creating and using the data• Data communications: exchange of data between two

users / devices via some form of transmission medium such as a wire cable– Delivery– Accuracy– Timeliness– Jitter

Five components of data communication

• Message• Sender• Receiver• Medium for transmission• Protocol: set of (explicit and implicit) rules

Data Representation

• Text: ASCII, Unicode, …• Numbers• Images• Audio• Video

Data flow (simplex, half- and full-duplex)

• Communication can be two-way by nature

2. NETWORKS

• Network: a set of devices (often referred to as users or nodes) connected by communication links– A node can be a computer, printer, or any other device

capable of sending and/or receiving data generated by other nodes on the network

• Performance of network– Throughput – Delay– Reliability (Accuracy and freq. of failures)– Security

Physical Structure of Network

• Types of connections– Point-to-point, multi-point

• Types of topologies– Mesh, star, bus, ring

• Covering areas– LAN, MAN, WAN

Types of connections

Categories of Topology

Mesh

Star Bus

Ring

Hybrid Topology

• Star + Bus

Covering AreaLAN: Local Area Network

WAN: Wide Area Network

MAN: Metropolitan Area Network – between LAN and WAN, e.g., Campus networks

Inter-network• A heterogeneous network made of four WANs

and two LANs

3. THE INTERNET

• Impact of “the Internet”– Revolutionized many aspects of our daily lives:

business, leisure, communications, …• History– ARPANET Project (1960s) led by Advanced

Research Project Agency (ARPA) in the Dept. of Defense (DoD) to establish reliable networks

– Evolves in 1970s and 1980s – TCP/IP

Hierarchical organization of the Internet

4. PROTOCOLS AND STANDARDS• Protocols: a set of rules for communications– Syntax – format – Semantics – meaning / interpretation– Timing – when data should be sent, and how fast

they can be sent• Standards– Essential in guaranteeing interoperability, and in

creating and maintaining an open and competitive market

Standards

• Two types– De facto: not formally approved, but everyone

accepts• MS Word (except Korea), MS Excel

– De jure: formally approved• WIPI (middleware platform in Korea)

• Standards Organizations– ISO, ITU-T, CCITT, ANSI, IEEE, EIA, …

• Internet Standards– Internet Draft, Request for Comment (RFC)

Homework

• Exercise in Chap. 1– 16– 17– 22– 25